The existence of dark matter density spike surrounding a black hole has been suggested for more than two decades. However, no smoking-gun evidence has been obtained from observations. Here, we show that the effect of dynamical friction due to dark matter density spike can satisfactorily explain the fast orbital decay in the two closest BH-LMXBs. The resultant spike index is \(\gamma =1.7-1.8\) , which is close to the value predicted by the stellar heating model (\(\gamma =1.5\) ) [1]}, [2]}. Although the BH-LMXBs considered here are not identical to the stellar heating scenario discussed in [2]}, recent simulations of the compact-object inspirals show that the motion of the companion object would affect the distribution of the dark matter density spike surrounding an intermediate-mass black hole, especially for the mass ratio \(q>10^{-3}\)  [4]}. Therefore, we may also see similar results of the stellar heating effect in the BH-LMXBs. Note that although the dark matter density is changing in time during re-distribution, the dynamical friction expression used in Eq. (1) is still applicable because the change is very slow in time [4]}. An overall consistent picture can be described as follows. When the black hole in a BH-LMXB is formed, the surrounding dark matter would be re-distributed to form a density spike (probably with an initial spike index \(\gamma \approx 2-2.5\) ) [6]}. However, the dynamical friction between dark matter and the companion star eventually help re-distribute the dark matter density spike again to reduce the spike index to approach \(\gamma =1.7-1.8\) . The orbital period is also decreasing with a fast rate \(\sim 1\)  ms yr\(^{-1}\)  due to dynamical friction. If the age of the black hole is larger than the heating time scale, the final spike index may change to a smaller value.
